At the moment AngelScript doesn't search for symbols in the parent namespaces. With the current implementation it is actually a bug that the script sees the string type inside the namespace. The script should behave as the registration does.

I'll look into implementing the search for symbols in the parent namespaces as soon as possible. I only held off on it because I wanted the basic namespace feature to mature enough before that, i.e. most of the bugs identified and fixed.